Thiazole-based flame retardant for polyamide vs. a sulfur-free flame retardant with similar phosphorus and nitrogen content

Polyamides are a promising candidate for the research of sulfur-containing flame retardants (FR). A new material based on 2-aminothiazole and 2-methyl-1,2-oxaphospholane-5-on-2-oxide is prepared and introduced into polyamide 12. To understand the effect of sulfur incorporation in its molecular structure, the new flame retardant is compared to a sulfur-free counterpart, revealing distinct variations in their self-extinguishing characteristics. The higher concentration of heteroatoms results in more flame diluting volatiles in the gas phase during thermal decomposition. The addition of the novel flame retardant containing phosphorus, nitrogen and sulfur, named TP, with only 5 m% into polyamide results in a UL-94 V-0 rating. Simultaneously, the limiting oxygen index increased to 31 %, compared to neat polyamide 12 with 24 %. Remarkably, the moisture absorption remains the same with the thiazole-based FR and the mechanical properties are only slightly decreased. This research reveals the flame retardant capabilities and advantages of a thiazole-based phosphorus compounds in polyamide.